Please explain .avi and .mpg

[boathouse]

Please can someone explain the difference between an .avi and .mpg file?

I understand the .mpg refers to the file being mpeg encoded and I believe that .avi files are a windows standard?

Why are DivX files always in .avi format?

Isn't .avi a bit limited because you cannot preview/playback the file until the whole download is finished - why don't all files come as .mpg?

Thanks for your help...

[AlanCake]

Hi

All the super hi tech dudes on this site could give you a precise 'techie' definition to this. I however, will break it down to 3 things:

1 A lets call it a 'standard' avi file is a video file which is uncompressed. Defining characteristics its big!

2 A mpeg video file is basically a compressed video file (much smaller than an 'standard' avi file).

3 DIVX files also have an avi extension - but they are no way related to the uncompressed AVI file in the first example. They are even more compressed than an mpeg file (smaller)

Hope this helps

Alan

[Spicuzza]

I'll try briefly from what I understand.

Audio Video Interleave seems to be a non standard format and seemingly everyone has a version of this file extension. With my ATI software I have 22 different types of AVI's to choose from for making a capture template. Except for uncompressed AVI and MJPEG, I have no clue as to what the other 20 are used for or in what circumstance they would be useful. I also don't care. It's my guess there must have been a computer audio/video format war and the winner was:

Moving Pictures Expert Group, fortunately for the most part the main file formats are MPEG-1 and MPEG-2.

If you want to simplify this video capture/edit/encode/burn stuff, first find a DVD player that plays (X)(S)VCD's @ 2500 kbps or more and on CD-RW's so you can experiment without out wasting countless disks.

Get a BIG dedicated HDD 120 gig would be great for video capture. Capture uncompressed AVI and encode that to MPEG @ 2000 to 2500 kbps or more and your video projects should come out with visual quality just under that of your source material.

[bugster]

Pretty much right AlanCake but I will take your explanation one step further. The file extension .avi stands for Audio Video Interleave and was, I believe, developed by Microsoft. In actual fact and AVI file can contain any combination of audio and video that you wish. The format simply specifies the data structures used to contain the two data streams and how they are interleaved together. The format also contains info in the header that describes how the two streams are to be rendered (i.e. what codecs are needed to decode the audio and/or video information present).

So, in short, a .avi file is simply a format for combining audio and video data into a single file.

Mpeg files may also contain (and usually do) multiplexed (or interleaved) audio and video streams. However in this case the streams are restricted to certain formats (mpeg1 or mpeg2 video, mpeg standard audio, maybe others, not sure) and the way the data is structured is different to avi.

Basically they are two different standards for storing audio and video in a single stream with the main difference being that mpeg is a specific compression standard whereas .avi can use any compression methods you wish (including no compression).

Hope this helps